BLANKING METHOD AND BLANKING CIRCUIT FOR COLOR BAR SIGNAL ON DISPLAY SCREEN

摘要

PURPOSE:To accurately measure and observe a chrominance signal by erasing an unnecessary luminous line from the screen of a cathode-ray tube by detecting the luminous line of a color bar signal through the differentiation of a demodulated signal. CONSTITUTION:Modulated signals are differentiated A, B to detect the parts of the signals where variation in terms of time is large, signals BL to lower luminance are supplied to the luminance modulation circuit of a cathode-ray tube during some period in term of the time when derivatives exist, thus the luminance of the tube is lowered as for the part of a luminous line to erase the line from the screen. In such a way, a luminous line unnecessary for the measurement and the adjustment of a chrominance signal can be erased from the screen, hence a luminous point is made easy to see, thus a highly accurate measurement can be executed.